Transparent article

ABSTRACT

An inspection method of transparent articles wherein presence or absence of optical inhomogeneities within the transparent articles can be accurately inspected is provided. 
     In an inspection method of transparent articles used in photolithography, for inspecting whether or not there are in homogeneities within transparent articles ( 4 ) formed of transparent material wherein optical properties regionally or locally change with regard to exposure light (specifically, interior defects  16 ), inspection light having a wavelength of 200 nm or shorter is introduced to the transparent article, and light ( 15 ) having a longer wavelength than the inspection light which is regionally or locally emitted is sensed on the optical path over which the inspection light is propagated within the transparent article, thereby detecting presence or absence of optical inhomogeneities within the transparent article.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. application Ser. No. 11/816,617 filed Aug.17, 2007, which is a 371 of PCT Application No. PCT/JP2006/302612 filedFeb. 15, 2006, and which claims benefit of Japanese Patent ApplicationNo. 2005-43134 filed Feb. 18, 2005, Japanese Patent Application No.2005-228598 filed Aug. 5, 2005 and Japanese Patent Application No.2005-244044 filed Aug. 25, 2005, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a transparent article formed of atransparent material having transparency as to light having an extremelypowerful energy such as an ArF excimer laser or F2 excimer laser forexample, regarding presence or absence of inhomogeneity wherein opticalproperties locally change within the transparent article as to thelight, and also relates to a glass substrate inspection method anddevice, and to a manufacturing method of glass substrates to be used asmask blanks wherein mask blank glass substrates are manufacturedfollowing inspection of interior defects of glass substrates, a maskblank manufacturing method using the mask blank glass substrates, and toan exposure mask manufacturing method using the mask blanks, and to themanufacturing method of a semiconductor device using the exposure masks.

BACKGROUND ART

In recent years, improved fineness of patterns formed on semiconductordevices has led to shorter wavelengths of exposure light used forphotolithography, i.e., ArF excimer laser (exposure wavelength of 193nm), and F2 excimer laser (exposure wavelength of 157 nm). With regardto exposure masks used for the photolithography, and mask blanks usedfor manufacturing the exposure masks, there has been rapid developmentfor opaque films for shielding the above-mentioned exposure wavelengthsof exposure light and phase shift films for phase shift thereof, whichare formed on transparent substrates for mask blanks (e.g., glasssubstrates), and various film materials have been proposed.

Also, exposure devices used in photolithography (e.g., steppers) haveoptical components such as lenses and the like, and materials withlittle absorption of exposure light, i.e., materials with good opticaltransparency are used for the optical components.

It is demanded of the mask blank transparent substrates and transparentarticles for manufacturing the mask blank transparent substrates (e.g.,synthetic quartz glass substrates) and optical components such as lensesand the like used in the exposure devices, that there be no opticalinhomogeneity therein (change in optical properties due to defects suchas foreign matter, bubbles, and so forth). Patent Document 1 discloses adetect detecting device and detect inspection method for detecting suchoptical inhomogeneity by irradiating a He—Ne laser into a glasssubstrate and detecting scattered light scattered by optical uniformitypresent within the glass substrate, e.g., the interior defects (foreignmatter, bubbles, and so forth), thereby detecting the aforementionedoptical uniformity.

-   Patent Document 1: Japanese Unexamined Patent Application    Publication (JP-A) No. 8-261953-   Patent Document 2: Japanese Unexamined Patent Application    Publication (JP-A) No. 8-31723-   Patent Document 3: Japanese Unexamined Patent Application    Publication (JP-A) No. 2003-81654

Problems to be Solved by the Invention

There are cases wherein, even with transparent substrates (e.g.,synthetic quartz glass substrates) and mask blank transparent substrates(e.g., mask blank glass substrates) regarding which determination hasbeen made by such a detect detecting device that there are no opticalinhomogeneities (e.g., interior defects), transfer pattern defects occurdue to transparent substrates as described later at the time oftransferring the pattern wherein a mask pattern for an exposure mask istransferred onto a semiconductor substrate using an ArF excimer laserwhich is the exposure light, leading to degradation of transferprecision. Also, there are cases wherein, in the same way as describedabove, transfer pattern defects owing to optical components occur at thetime of pattern transfer with the optical components such as lenses andthe like used in the exposure device, thereby leading to degradation oftransfer precision.

The reason is thought to be that, even in the event that there is nooptical change such as scattering when using visible light laser such asthe He—Ne laser as the inspection light, at the time of performingactual pattern transfer using high-energy light such as ArF excimerlaser and F2 excimer laser as the exposure light, there are opticalinhomogeneities (interior defects originated by local striae,inclusions, foreign matter, for example) present in the transparentsubstrate or optical components, causing regional (or local) change inoptical properties (e.g., drop of transmissivity, change in phasedifference).

The present invention has been made in light of the above situation, andaccordingly it is an object thereof to provide an inspection method forinspecting a transparent article such as optical components of exposuredevices and substrates for exposure masks, used in photolithography,regarding presence or absence of inhomogeneity in optical propertiesgreatly affecting pattern transfer to a transfer medium.

Another object of the present invention is to provide a semiconductordevice manufacturing method whereby the transfer precision of a patterntransfer onto semiconductor substrates can be suitably realized, anexposure mask and a manufacturing method thereof wherein the transferprecision of pattern transfer onto a transfer medium to manufacture thesemiconductor device is suitable, a manufacturing method of a mask blankfor manufacturing the exposure mask and a manufacturing method thereof,and a mask blank transparent substrate for manufacturing the mask blankand the manufacturing method thereof.

Means to Solve the Problems

According to this invention, an inspection method is for inspecting atransparent article formed of a transparent material used forphotolithography, regarding presence or absence of inhomogeneity whereinoptical properties regionally or locally change within the transparentarticle as to exposure light; wherein inspection light having awavelength of 200 nm or shorter is introduced into the transparentarticle, and light having a wavelength longer than that of theinspection light that has been generated regionally or locally isdetected on the optical path over which the inspection light ispropagated within the transparent article, thereby inspecting forpresence or absence of optical inhomogeneity in the transparent article.

According to this invention, the inspection method is for inspecting atransparent article, wherein the light having a wavelength longer thanthat of the inspection light has a wavelength exceeding 200 nm and up to600 nm.

According to this invention, the inspection method is for inspecting atransparent article, wherein the transparent article is either anoptical component of an exposure device used for photolithography, or asubstrate of an exposure mask used for photolithography.

According to this invention, the inspection method is for inspecting atransparent article, wherein the optical component or the exposure masksubstrate are formed of synthetic quartz glass.

According to this invention, the inspection method is for inspecting atransparent article, wherein, at the time of introducing the inspectionlight to the transparent article, the inspection light is introduced tothe transparent article in a state wherein causative substance whichcauses damage to the surface of the transparent article uponintroduction of the inspection light is eliminated from the ambientatmosphere of the transparent article.

According to this invention, the inspection method is for inspecting atransparent article 5, wherein the energy of the inspection light perunit area is 10 mJ/cm² or greater but 50 mJ/cm² or smaller per pulse.

According to this invention, a manufacturing method is of a transparentsubstrate for a mask blank, the method comprising a preparation step forpreparing a transparent substrate for a mask blank, having a surfacefrom which inspection light having a wavelength of 200 nm or shorter isintroduced; an inspection step wherein inspection light is introducedfrom one side of the surface, and light having a wavelength longer thanthat of the inspection light that is generated regionally or locally isdetected on the optical path over which the inspection light ispropagated within the transparent article, thereby inspecting forpresence or absence of optical inhomogeneity in the transparent article;and a determining step for determining whether or not the transparentsubstrate will generate no transfer pattern defects due to regional orlocal optical property changes, based on the present or absence of theinhomogeneity.

According to this invention, the manufacturing method is of atransparent substrate for a mask blank, wherein the light having awavelength longer than that of the inspection light has a wavelengthexceeding 200 nm and up to 600 nm.

According to this invention, the manufacturing method is of atransparent substrate for a mask blank, wherein the principal surface ofthe transparent substrate is subjected to precision polishing followingthe determining step, thereby obtaining a transparent substrate for amask blank.

According to this invention, the manufacturing method is of atransparent substrate for a mask blank, wherein, at the time ofintroducing the inspection light to the transparent article, theinspection light is introduced to the transparent article in a statewherein causative substance which causes damage to the surface of thetransparent article upon introduction of the inspection light iseliminated from the ambient atmosphere of the transparent article.

According to this invention, the manufacturing method is of atransparent substrate for a mask blank 0, wherein the surface whereinthe inspection light is introduced is a side face orthogonal to theprincipal surface of the transparent substrate upon which a thin film toserve as a mask pattern is formed.

According to this invention the manufacturing method is of a transparentsubstrate for a mask blank, wherein, in the inspection step, inspectionlight having a beam shape greater than the width of the side face isintroduced to the surface.

According to this invention, the manufacturing method is of atransparent substrate for a mask blank, wherein the energy of theinspection light per unit area is 10 mJ/cm² or greater but 50 mJ/cm² orsmaller per pulse.

According to this invention, a manufacturing method is for a mask blank,wherein a thin film to serve as a mask pattern is formed on theprincipal surface of a transparent substrate for a mask blank obtainedby the manufacturing method of a transparent substrate for a mask blank,thereby manufacturing a mask blank.

According to this invention, a manufacturing method is for an exposuremask, wherein the thin film on the mask blank is patterned so as to forma mask pattern on the principal surface of the transparent substrate fora mask blank, thereby manufacturing an exposure mask.

According to this invention, a manufacturing method is for asemiconductor device, wherein an exposure mask obtained by themanufacturing method for an exposure mask is used to transfer a maskpattern formed on an exposure mask onto a resist film to manufacture asemiconductor device.

According to this invention a transparent substrate is for a mask blank,wherein upon introduction of light having a wavelength of 200 nm orshorter from one side of the surface of the transparent substrate, theloss of light having a wavelength longer than the wavelength that isgenerated regionally or locally within the transparent substrate is8%/cm or lower within the mask pattern formation region of thetransparent substrate.

According to this invention, the transparent substrate is for a maskblank wherein the transparent substrate for a mask blank is atransparent substrate for a phase-shift mask blank.

According to this invention, the transparent substrate is for a maskblank wherein the loss of light having a wavelength longer than thewavelength that is generated regionally or locally within thetransparent substrate is 3%/cm or lower within the mask patternformation region of the transparent substrate.

According to this invention, a mask blank, wherein a thin film to serveas a mask pattern, or a thin film for forming a mask pattern, is formedon the principal surface of the transparent substrate for a mask blank.

According to this invention an exposure mask wherein the thin film toserve as a mask pattern on the mask blank is patterned to form a maskpattern of a thin film pattern on the principal surface of thetransparent substrate for a mask blank.

According to this invention an exposure mask wherein the thin film toform a mask pattern on the mask blank is patterned to form a thin filmpattern, and the thin film pattern is used as a mask to etch thetransparent substrate for a mask blank, thereby forming a mask patternon the principal surface of the transparent substrate.

ADVANTAGES

With the invention, in an inspection method for inspecting a transparentarticle formed of a transparent material used for photolithography,regarding presence or absence of inhomogeneity wherein opticalproperties regionally or locally change within the transparent articleas to exposure light; inspection light having a wavelength of 200 nm orshorter is introduced into the transparent article, and light having awavelength longer than that of the inspection light that is generatedregionally or locally is detected on the optical path over which theinspection light is propagated within the transparent article, therebyinspecting for presence or absence of optical inhomogeneity in thetransparent article, thereby enabling accurate inspection for presenceor absence of interior defects which greatly affect pattern transfer toa transfer medium.

Now, in the event that the transparent article is an optical componentof an exposure device used for photolithography, or for manufacturing asubstrate of an exposure mask used for photolithography (transparentsubstrate for a mask blank), the exposure mask manufactured via thissubstrate for exposure mask and mask blank, and optical component of theexposure device do not have regionally or locally opticallyinhomogeneous regions, so at the time of using the exposure mask oroptical component and exposure light to transfer the mask pattern of theexposure mask onto the transfer medium, there is no region whereinoptical properties change (e.g., drop of transmissivity) due toregionally or locally optically inhomogeneity, so excellent transferprecision can be obtained without transfer pattern defects on thetransfer medium due to adverse affects thereof on the pattern transfer.

With the invention, accurate inspection for presence or absence ofinterior defects which greatly affect pattern transfer to a transfermedium can be performed while preventing damage to the surface of thetransparent article.

At the time of introducing the inspection light to the transparentarticle, the inspection light is introduced to the transparent articlein a state wherein causative substance (e.g., floating particles) or thelike which causes damage to the surface of the transparent article uponintroduction of the inspection light is eliminated from the ambientatmosphere of the transparent article, so damage to the surface whichoccurs due to adhering matter and deposited matter adhering to thesurface of the transparent article regionally or locally making thetemperature of the surface high can be prevented.

With the invention, the energy of the inspection light per unit area is10 mJ/cm² or greater but 50 mJ/cm² or smaller per pulse, so generationof plasma at the surface of the transparent article due to theinspection light can be avoided, and the intensity of wavelengths havinga longer wavelength than the inspection light which is generated fromoptical inhomogeneities upon introduction of the inspection light issufficiently ensured, so detection precision of inhomogeneity can bemaintained high.

With the invention, a transparent substrate for a mask blank ismanufactured via a preparation step for preparing a transparentsubstrate for a mask blank, having a surface from which inspection lighthaving a wavelength of 200 nm or shorter is introduced; an inspectionstep wherein inspection light is introduced from one side of thesurface, and light having a wavelength longer than that of theinspection light that is generated regionally or locally is detected onthe optical path over which the inspection light is propagated withinthe transparent article, thereby inspecting for presence or absence ofoptical inhomogeneity in the transparent article; and a determining stepfor determining whether or not the transparent substrate will generateno transfer pattern defects due to regional or local optical propertychanges, based on the presence or absence of the inhomogeneity, so thereis no region wherein optical properties change (e.g., drop oftransmissivity) due to regionally or locally optically inhomogeneity,and excellent transfer precision can be obtained without transferpattern defects on the transfer medium due to adverse affects thereof onthe pattern transfer.

With the invention optical in homogeneity of the transparent substrateis detected at an early stage prior to precision polishing of theprincipal surface in the manufacturing process of the transparentsubstrate for a mask blank, so the principal surface is subjected toprecision polishing only for transparent substrates wherein there is nooptical inhomogeneity, thereby avoiding the waste of performingprecision polishing on transparent substrates with opticalinhomogeneity.

With the invention, a transparent substrate for a mask blank with nooptical inhomogeneity which greatly affects pattern transfer to atransfer medium can be obtained without damage to the surface of thetransparent substrate for a mask blank due to introduction of inspectionlight.

With the invention, in addition to the advantages obtained by theinvention, there is the advantage of removing foreign matter andcontaminants adhering to the principal surface of the transparentsubstrate for a mask blank.

With the invention, a transparent substrate for a mask blank with nooptical inhomogeneity which greatly affects pattern transfer to atransfer medium can be obtained without damage due to generation ofplasma at the surface of the transparent substrate for a mask blank dueto introduction of inspection light.

With the invention, a transparent substrate for a mask blank obtained bythe manufacturing method of a transparent substrate for a mask is usedto manufacture a mask blank, the thin film on the mask blank ispatterned so as to manufacture an exposure mask, and the exposure maskis used to manufacture a semiconductor device. Accordingly, at the timeof using the exposure mask to transfer the mask pattern of the exposuremask onto the transfer medium (semiconductor substrate), there is noregion wherein optical properties change (e.g., drop of transmissivity)due to regionally or locally optically inhomogeneity in the transparentsubstrate used for the exposure mask, so transfer precision can beimproved without transfer pattern defects on the transfer medium due toadverse affects thereof on the pattern transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A manufacturing process diagram illustrating an embodiment of themanufacturing method of a glass substrate for a mask blank,manufacturing method for a mask blank, and manufacturing method for anexposure mask, according to the present invention.

FIG. 2 A perspective view illustrating an embodiment of a defectinspection device for the glass substrate according to the presentinvention.

FIG. 3 A graph illustrating intensity distribution of received lightsubjected to image processing with a computer.

FIG. 4 Views showing ArF excimer laser light guided from a laserirradiation device shown in FIG. 2 and a synthetic quartz glasssubstrate, wherein (A) is a frontal view and (B) is a side view.

FIG. 5 A schematic frontal view illustrating the overall configurationof the defect inspection device in FIG. 2.

FIG. 6 A manufacturing process diagram illustrating another embodimentof the manufacturing method of a glass substrate for a mask blank,manufacturing method for a mask blank, and manufacturing method for anexposure mask, according to the present invention.

FIG. 7 A perspective view illustrating another embodiment of the defectinspection device for the glass substrate according to the presentinvention.

FIG. 8 A schematic side view illustrating a sputtering device used inthe manufacturing process of the mask blank in FIG. 1.

FIG. 9 A side view illustrating the position relation between thesputtering target and glass substrate for mask blank in FIG. 8.

REFERENCE NUMERALS

-   -   20 defect inspecting device    -   21 laser irradiation device    -   22 XYZ stage    -   23 CCD camera    -   24 detection field    -   26 USB cable    -   27 computer    -   4 synthetic quartz glass substrate    -   16 interior defect

BEST MODE FOR CARRYING OUT THE INVENTION

As specific means for solving the above problems, the present inventionemploys the following configuration.

(Configuration 1-1)

A defect inspection method for a glass substrate, wherein light of anexposure wavelength is introduced from one side of a surface of a glasssubstrate, light of a wavelength longer than the exposure wavelengththat is generated at interior defects of the glass substrate by theintroduced light of the exposure wavelength is received at the otherside of the surface, and interior defects of the glass substrate aredetected based on the amount of light received.

(Configuration 1-2)

The defect inspection method for a glass substrate according toConfiguration 1-1, wherein the wavelength of the light introduced intothe glass substrate is 200 nm or shorter.

(Configuration 1-3)

A defect inspection device for a glass substrate, including lightintroducing means for introducing light of an exposure wavelength fromone side of a surface of a glass substrate, light receiving means forreceiving light of a wavelength longer than the exposure wavelength thatis generated at interior defects of the glass substrate by theintroduced light of the exposure wavelength, at the other side of thesurface, and detecting means for detecting interior defects of the glasssubstrate, based on the amount of light received by the light receivingmeans.

(Configuration 1-4)

The defect inspection device for a glass substrate according toConfiguration 1-3, wherein the wavelength of the light introduced intothe glass substrate is 200 nm or shorter.

(Configuration 1-5)

A manufacturing method for a glass substrate for a mask blank,including: a preparation step for preparing a synthetic quartz glasssubstrate having a surface from which light of an exposure wavelength isintroduced; and a detecting step wherein light of the exposurewavelength is introduced from one side of the surface and light of awavelength longer than the exposure wavelength that is generated atinterior defects of the glass substrate by the introduced light of theexposure wavelength is received at the other side of the surface,whereby interior defects of the glass substrate are detected based onthe intensity of light received; wherein glass substrates for maskblanks are manufactured using the synthetic quartz glass substratesregarding which interior defects have not been detected in the detectingstep.

(Configuration 1-6)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 1-5, wherein the wavelength of the lightintroduced into the glass substrate is 200 nm or shorter.

(Configuration 1-7)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 1-5 or Configuration 1-6, wherein theprincipal surface of the synthetic quartz glass substrate is subjectedto precision polishing following the detecting step, thereby obtaining aglass substrate for a mask blank.

(Configuration 1-8)

A manufacturing method for a mask blank, wherein a thin film to serve asa mask pattern is formed on the principal surface of the glass substratefor a mask blank obtained by the manufacturing method of a glasssubstrate for a mask blank according to any one of Configuration 1-5through Configuration 1-7.

(Configuration 1-9)

A manufacturing method for an exposure mask wherein the thin film on themask blank according to Configuration 1-8 is patterned so as to form amask pattern on the principal surface of the glass substrate for a maskblank, thereby manufacturing an exposure mask.

With the invention according to any one of Configuration 1-1 throughConfiguration 1-4, light of an exposure wavelength is introduced fromone side of a surface of a glass substrate, light of a wavelength longerthan the exposure wavelength that is generated at interior defects ofthe glass substrate by the introduced light of the exposure wavelengthis received at the other side of the surface, and interior defects ofthe glass substrate are detected based on the intensity of lightreceived, so using light of an exposure wavelength for inspectinginterior defects of glass substrates enables interior defects whichwould lead to transfer pattern defects at the time of pattern transferto be detected well.

Now, in the event that the glass substrate is for manufacturing a glasssubstrate for a mask blank, there are no interior defects in an exposuremask glass substrate manufactured via the glass substrate for a maskblank and the mask blank, so at the time of performing pattern transferwherein the mask pattern of the exposure mask is transferred onto atransfer medium using the exposure mask and exposure light, there is noregion wherein optical properties regionally change (e.g., drop oftransmissivity), so excellent transfer precision can be obtained withouttransfer pattern defects on the transfer medium due to adverse affectsthereof on the pattern transfer.

With the invention according to Configuration 1-5 or Configuration 1-6,light of the exposure wavelength is introduced from one side of thesurface of a synthetic quartz glass substrate, light of a wavelengthlonger than the exposure wavelength that is generated at interiordefects of the glass substrate by the introduced light of the exposurewavelength is received at the other side of the surface, interiordefects of the glass substrate are detected based on the intensity oflight received, and glass substrates for mask blanks are manufacturedusing the synthetic quartz glass substrates regarding which interiordefects have not been detected, so there are no interior defects in theglass substrates for exposure masks manufactured via the glass substratefor a mask blank and the mask blank. Accordingly, at the time ofperforming pattern transfer wherein the mask pattern of the exposuremask is transferred onto a transfer medium using the exposure mask andexposure light, there is no region wherein optical properties regionallychange (e.g., drop of transmissivity), so excellent transfer precisioncan be obtained without transfer pattern defects due to adverse affectsthereof on the pattern transfer.

With the invention according to Configuration 1-7, interior defects inthe quartz glass substrate are detected at an early stage prior toprecision polishing of the principal surface in the manufacturingprocess of the glass substrate for a mask blank, so the principalsurface is subjected to precision polishing only for quartz glasssubstrates wherein there is no interior defect, thereby avoiding thewaste of performing precision polishing on quartz glass substrates withinterior defects.

With the invention according to Configuration 1-8 or Configuration 1-9,a glass substrate for a mask blank obtained by the manufacturing methodof a glass substrate for a mask blank according to any one ofConfigurations 1-5 through 1-7 is used to manufacture a mask blank, thethin film on the mask blank is patterned so as to manufacture anexposure mask, so at the time of using the exposure mask to transfer themask pattern of the exposure mask onto the transfer medium, there is noregion wherein optical properties regionally change (e.g., drop oftransmissivity) since a quartz glass substrate wherein there are nointerior defects is used, and excellent transfer precision can beobtained without transfer pattern defects due to adverse affects thereofon the pattern transfer.

As specific means for solving the above problems, the present inventionfurther employs the following configuration.

(Configuration 2-1)

A manufacturing method for a glass substrate for a mask blank including:a preparation step for preparing a synthetic quartz glass substratehaving a surface from which short-wavelength light having a wavelengthof 200 nm or shorter is introduced; and a detecting step for introducingthe short-wavelength light from the surface of the synthetic quartzglass substrate, receiving long-wavelength light of a wavelength longerthan the short-wavelength light that is generated at interior defects ofthe glass substrate at the other side of the surface, and detecting theinterior defects based on the received long-wavelength light; with glasssubstrates for mask blanks being manufactured using the quartz glasssubstrates in which no interior defects are detected in the detectingstep; wherein, in the detecting step, at the time of introducing theshort-wavelength light to the quartz glass substrate, theshort-wavelength light is introduced to the quartz glass substrate in astate in which causative substance which causes damage to the surface ofthe glass substrate upon introduction of the short-wavelength light iseliminated from the ambient atmosphere of the glass substrate.

(Configuration 2-2)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 2-1, wherein the state in which causativesubstance is eliminated from the ambient atmosphere of the quartz glasssubstrate is an atmosphere wherein clean air circulates.

(Configuration 2-3)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 2-1 or Configuration 2-2, wherein theatmosphere wherein clean air circulates is an atmosphere of a cleannessexceeding that of ISO Class 5.

(Configuration 2-4)

The manufacturing method for a glass substrate for a mask blankaccording to any one of Configuration 2-1 through Configuration 2-3,wherein the atmosphere wherein clean air circulates is generated by airpassing through a chemical filter.

(Configuration 2-5)

The manufacturing method for a glass substrate for a mask blankaccording to any one of Configuration 2-1 through Configuration 2-4,wherein the maximum height (Rmax) of the surface of the synthetic quartzsubstrate into which the short-wavelength light is introduced is 0.5 μmor lower.

(Configuration 2-6)

A manufacturing method for a mask blank, wherein a thin film to serve asa mask pattern is formed on the principal surface of the glass substratefor a mask blank obtained by the manufacturing method of a glasssubstrate for a mask blank according to any one of Configuration 2-1through Configuration 2-5.

(Configuration 2-7)

A manufacturing method for an exposure mask wherein the thin film on themask blank according to Configuration 2-6 is patterned so as to form amask pattern on the principal surface of the glass substrate for a maskblank, thereby manufacturing an exposure mask.

With the invention according to any one of Configuration 2-1 throughConfiguration 2-5, short-wavelength light having a wavelength of 200 nmor shorter is introduced to the synthetic quartz glass substrate, andthe short-wavelength light is used for inspection of interior defects inthe synthetic quartz glass substrate (glass substrate for a mask blank),so interior defects which would lead to transfer pattern defects at thetime of pattern transfer using the exposure mask manufactured from thisglass substrate, and exposure light, can be detected well.

At the time of introducing the short-wavelength light which is theinspection light to the synthetic quartz glass substrate, the inspectionlight is introduced to the glass substrate in a state wherein causativesubstance (e.g., floating particles) or the like which causes damage tothe surface of the glass substrate upon introduction of theshort-wavelength light is eliminated from the ambient atmosphere of theglass substrate, so damage to the surface which occurs due to adheringmatter and deposited matter adhering to the surface of the syntheticquartz glass substrate regionally or locally making the temperature ofthe surface high can be prevented. Particularly, forming the maximumheight (Rmax) of the surface of the synthetic quartz substrate intowhich the inspection light is introduced so as to be 0.5 μm or lowermakes adhesion of causative substances which generate damage moredifficult, so damage to the surface can be further prevented.

Also, according to the Configuration 2-6 or Configuration 2-7, a maskblank is manufactured using the glass substrate for a mask blankobtained by the manufacturing method for a glass substrate for a maskblank according to any one of Configuration 2-1 through Configuration2-5, and the thin film on the mask blank is patterned so as to form anexposure mask. Accordingly, at the time of pattern transferring whereinthe mask pattern of the exposure mask is transferred to a transfermedium using the exposure mask, a synthetic quartz glass substratewherein there are no interior defects and no damage on the surface isused, so there is no region where optical properties regionally change(e.g., drop of transmissivity) due to the interior defects or thedamage, and transfer precision can be improved without adverse effect onpattern transfer leading to transfer pattern defects.

Also, as specific means for solving the above problems, the presentinvention employs the following configuration.

(Configuration 3-1)

A manufacturing method for a glass substrate for a mask blank including:a preparation step for preparing a synthetic quartz glass substratehaving a surface including one end face from which short-wavelengthlight having a wavelength of 200 nm or shorter is introduced; and adetecting step for introducing the short-wavelength light from the oneend face, receiving long-wavelength light of a wavelength longer thanthe short-wavelength light that is generated at interior defects of theglass substrate at the other side of the surface, and detecting theinterior defects based on the received long-wavelength light; with glasssubstrates for mask blanks being manufactured using the quartz glasssubstrates in which no interior defects have been detected in thedetecting step; wherein, in the detecting step, the short-wavelengthlight having a beam shape larger than the width of the one end face isintroduced to the one end face.

(Configuration 3-2)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 3-1, wherein the end face is a side faceorthogonal to the principal surface of the glass substrate upon whichthe thin film to serve as the mask pattern is to be formed, and achamfered face between the side face and the principal surface.

(Configuration 3-3)

The manufacturing method for a glass substrate for a mask blankaccording to Configuration 3-1 or Configuration 3-2, wherein the energyof the short-wavelength light per unit area is 10 mJ/cm² or greater but50 mJ/cm² or smaller (per pulse).

(Configuration 3-4)

The manufacturing method for a glass substrate for a mask blankaccording to any one of Configuration 3-1 through Configuration 3-3,wherein, at the one end face of the synthetic quartz glass substrate,the short-wavelength light is scanned in the longitudinal direction ofthe one end face.

(Configuration 3-5)

A manufacturing method for a mask blank, wherein a thin film to serve asa mask pattern is formed on the principal surface of the glass substratefor a mask blank obtained by the manufacturing method of a glasssubstrate for a mask blank according to any one of Configuration 3-1through Configuration 3-4.

(Configuration 3-6)

A manufacturing method for an exposure mask wherein the thin film on themask blank according to Configuration 3-5 is patterned so as to form amask pattern on the principal surface of the glass substrate for a maskblank, thereby manufacturing an exposure mask.

With the invention according to Configuration 3-1 or Configuration 3-2,short-wavelength light having a wavelength of 200 nm or shorter isintroduced to the synthetic quartz glass substrate, and theshort-wavelength light is used for inspection of interior defects in thesynthetic quartz glass substrate (glass substrate for a mask blank), sointerior defects which would lead to transfer pattern defects at thetime of pattern transfer using the exposure mask manufactured from thisglass substrate, and exposure light, can be detected well.

Also, the beam shape of the short-wavelength light is set to be largerthan the width of the one end face of the synthetic quartz glasssubstrate into which the short-wavelength light is introduced, so theenergy (per pulse) of the short-wavelength light per unit area at theone end face is not too strong, thereby preventing plasma from occurringaround the one end face. Consequently, a situation wherein contaminationor foreign matter or the like adhering to the one end face damages theone end face due to plasma can be prevented.

With the invention according to Configuration 3-3, the energy of theshort-wavelength light per unit area introduced to the one end face ofthe synthetic quartz glass substrate is 10 mJ/cm² or greater but 50mJ/cm² or smaller (per pulse), so generation of plasma at the one endface due to this short-wavelength light can be avoided, and also theintensity of the long-wavelength light generated at interior defects dueto introduction of the short-wavelength light is sufficiently ensured,and accordingly reliability of defect detection precision can bemaintained.

With the invention according to Configuration 3-4, at the one end faceof the synthetic quartz glass substrate, the short-wavelength light isscanned in the longitudinal direction of the one end face, so theshort-wavelength light is irradiated on both principal surfacescontiguous to this one end face. Accordingly, particles and contaminantsadhering to these both principal surfaces can be removed by theshort-wavelength light.

Also, according to the Configuration 3-5 or Configuration 3-6, a maskblank is manufactured using the glass substrate for a mask blankobtained by the manufacturing method for a glass substrate for a maskblank according to any one of Configuration 3-1 through Configuration3-4, and the thin film on the mask blank is patterned so as to form anexposure mask. Accordingly, at the time of pattern transferring whereinthe mask pattern of the exposure mask is transferred to a transfermedium using the exposure mask, a synthetic quartz glass substratewherein there are no interior defects and no damage on the surface isused, so there is no region where optical properties regionally change(e.g., drop of transmissivity) due to the interior defects or thedamage, and transfer precision can be improved without adverse effect onpattern transfer leading to transfer pattern defects.

Now, the best mode for carrying out the invention for the manufacturingmethod for a glass substrate for a mask blank, the manufacturing methodfor a mask blank, and the manufacturing method for an exposure mask,will be described with reference to the drawings, by way of example of atransparent substrate for a mask blank, more specifically a glasssubstrate for a mask blank. Note that in the following, the exposurelight and inspection light will be described as an ArF excimer laserlight (wavelength: 193 nm) with an exposure light wavelength andinspection light wavelength of 200 nm or shorter.

[A] Manufacturing Method for Glass Substrate for Mask Blank

With reference to FIG. 1, a synthetic quartz glass plate 1 (FIG. 1( a))cut out to a size of approximately 152 mm×approximately 152mm×approximately 6.5 mm or approximately 152.4 mm×approximately 152.4mm×approximately 6.85 mm from a synthetic quartz glass ingotmanufactured according to a manufacturing method disclosed in PatentDocument 2 (Japanese Unexamined Patent Application Publication No.8-31723) or Patent Document 3 (Japanese Unexamined Patent ApplicationPublication No. 2003-81654) is subjected to chamfering, and next, theprincipal surfaces 5 and 6 which are the surfaces of the syntheticquartz glass plate 1 and the end faces 2 and 3 (end faces are formed ofthe side faces orthogonal to the principal surfaces 5 and 6, andchamfered faces (not shown) formed between the principal surfaces andthe side faces) are polished to a mirror surface of a degree whereinspection light (ArF excimer laser light) which is also exposure lightwavelength light can be introduced, thereby preparing a synthetic quartzglass substrate 4 (FIG. 1 (b)). In this preparation step, the surfaceroughness Ra (arithmetic average roughness) of the principal surfaces 5and 6 of the synthetic quartz glass substrate 4 is approximately 0.5 nmor smaller, and the surface roughness Ra (arithmetic average roughness)of the end faces 2 and 3 (side faces and chamfered faces) isapproximately 0.03 nm or smaller.

Next, a detecting step is performed wherein the synthetic quartz glasssubstrate 4 is mounted on a defect detecting device 20 for glasssubstrates shown in FIG. 2, the ArF excimer laser light is introducedfrom one end face 2 of the synthetic quartz glass substrate 4, and light(fluorescence) 15 of a wavelength longer than that of the ArF excimerlaser light, that is generated by an interior defect 16 which is opticalinhomogeneity present within the synthetic quartz glass substrate 4 isreceived by photoreceptor means (CCD camera 23) from one principalsurface 5 of the synthetic quartz glass substrate 4, along with light(fluorescence) 17 of a wavelength longer than that of the ArF excimerlaser light generated by regions other than the interior defects 16 ofthe synthetic quartz glass substrate 4, thereby detecting the interiordefects 16 based on difference in light amount (intensity) between thereceived light 15 and 17.

Now, of the interior defects 16 present in the synthetic quartz glasssubstrate 4, there are interior defects 16 such as local striae,inclusions, foreign matter, and so forth, which are not problematic inthe case that the exposure light is of an exposure light sourceexceeding a wavelength of 200 nm (e.g., KrF excimer laser (exposurelight wavelength: 248 nm), but are problematic in cases of exposurelight wavelength of 200 nm or shorter as with ArF excimer laser. Theseinterior defects 16 all cause regional or local optical property changes(e.g., drop of transmissivity or change in phase difference) at the timeof pattern transfer wherein the mask pattern of the exposure mask 14 istransferred onto a transfer medium using the exposure mask 14manufactured from the synthetic quartz glass substrate 4 via the maskblank glass substrate 7 and mask blank 9, and the exposure light ofwhich the exposure light wavelength is 200 nm or shorter. This leads toadverse effects on the pattern transfer and degrading transferprecision. This ultimately becomes a transfer pattern defect of thetransfer medium (e.g., semiconductor device) (in the semiconductormedium, a circuit pattern defect).

The aforementioned “local striae” is a region wherein a metal elementhas become melted into the synthetic quartz glass in minute quantitiesat the time of synthesizing the synthetic quartz glass. In the eventthat there is such local striae in the glass substrate 7 for the maskblank for the exposure mask 14, transmissivity will drop 20 to 40% atthe time of pattern transfer, degrading transfer precision, andultimately resulting in a transfer pattern defect. Also, theaforementioned “inclusions” is a region wherein a metal element hasbecome melted into the synthetic quartz glass in quantities greater thanwith local striae. In the event that there is such contents in the glasssubstrate 7 for the mask blank for the exposure mask 14, transmissivitywill drop approximately 40 to 60% at the time of pattern transfer,degrading transfer precision, and ultimately resulting in a transferpattern defect. On the other hand, “foreign matter” is anoxygen-excessive region wherein oxygen has become melted in thesynthetic quartz glass in excessive quantities, and does not recoverfollowing irradiation of high-energy light. In the event that there issuch foreign matter in the glass substrate 7 for the mask blank for theexposure mask 14, transmissivity will drop approximately 5 to 15% at thetime of pattern transfer, deteriorating transfer precision, andultimately resulting in a transfer pattern defect. Interior defects 16which are regional optical inhomogeneities which cause transfer patterndefects at the time of pattern transfer are not restricted to theaforementioned “local striae”, “inclusions”, and “foreign matter”.Optical inhomogeneity wherein loss due to fluorescence generated locallyor regionally within the substrate at the time of introducing light,having a wavelength of 200 nm or shorter which is the inspection lightor exposure light, to the glass substrate for a mask blank, exceeds8%/cm, should be taken as an interior defect 16. That is to say, maskblank glass substrates 7 with optical loss within the mask blank glasssubstrate 7 of 8%/cm or less should be selected in the detecting step.Particularly, in the case of mask blank glass substrates used for phaseshift masks, mask blank glass substrates 7 with optical loss of 3% orless should be selected in the detecting step.

An interior defect 16 which causes regional or local changes in opticalproperties which lead to the aforementioned transfer pattern defects,will generate light (fluorescence) 15 having a wavelength longer thanthe wavelength of the ArF excimer laser light when introducing the ArFexcimer laser to the mask blank glass substrate 7. Wavelengths of thefluorescence 15 generated from the interior defect 16 which will becomea transfer pattern defect are longer than 200 nm but 600 nm or shorter,and include violet (wavelength of 400 to 435 nm), blue (wavelength of435 to 480 nm), cyan (wavelength of 480 to 490 nm), blue-green(wavelength of 490 to 500 nm), green (wavelength of 500 to 560 nm),yellow-green (wavelength of 500 to 580 nm), and yellow (wavelength of580 to 595 nm). Identification of interior defects 16 by suchfluorescence can be made by visually recognizing difference in colorbetween the light 15 and light 17, or detecting difference in spectralproperties and/or quantity of light with a spectroscope.

A defect inspecting device 20 for the glass substrate on whichinspection step is to be performed is for sensing or detecting theabove-described interior defects 16 (regional striae, inclusions,foreign matter, etc., causing local change in optical properties at thetime of pattern transfer). The defect inspecting device 20 includes alaser irradiation device 21 serving as light introducing means forintroducing ArF excimer laser light which is light of the exposurewavelength (i.e., light of the same wavelength as the exposurewavelength) from the end face 2 of the synthetic quartz glass substrate4, and XYZ stage 22 upon which the synthetic quartz glass substrate 4 isplaced in moved in the X direction, Y direction, and Z direction, as tothe laser light emitted from the laser irradiation device 21, and a CCDdevice and a lens for widening the detection range of the CCD device(both unshown) disposed on the principal surface 5 side of the syntheticquartz glass substrate 4 placed on the XYZ stage 22, and has a CCDcamera (line sensor camera) 23 serving as photoreceptor means having adetection field 24 over the entire range of the width direction of thesynthetic quartz glass substrate 4 (i.e., the irradiation direction ofthe laser light irradiated from the laser irradiation device 21), and acomputer 27 serving as detecting means, connected to the CCD camera 23using a USB cable 26.

The laser irradiation device 21 sequentially introduces the ArF excimerlaser light from each position in the Y direction at the end face 2 ofthe synthetic quartz glass substrate 4 (i.e., the longitudinal directionof the end face 2), while the XYZ stage 22 moves the synthetic quartzglass substrate 4 in the Y direction. The laser irradiation device 21may be that which emits ArF excimer laser light of a beam shape of 7.0mm×4.0 mm which is larger than the width of the end face 2 for example,energy of 6 mJ per pulse, energy per unit area of 21.4 mJ/cm², and afrequency of 50 Hz, to the end face 2 which has been polished to amirror. Also, the CCD camera 23 receives and captures light from theprincipal surface 5 side of the synthetic quartz glass substrate 4 foreach position in the Y direction of the synthetic quartz glass substrate4, regarding the light 15 and 17 having a wavelength longer than thewavelength λ1, which the synthetic quartz glass substrate 4 emits due tothe ArF excimer laser light (wavelength of λ1) being irradiated intoeach position in the Y direction at the end face 2 of the syntheticquartz glass substrate 4. With the present embodiment, the CCD camera 23is a monochrome camera which receives and captures contrast of the light15 and 17.

The computer 27 inputs the images from the CCD camera 23 and performsimage processing for each position in the Y direction of the syntheticquartz glass substrate 4, and analyzes the quantity of light (intensity)of the light 15 and 17 received by the CCD camera 23 with regard to theX directional position of the synthetic quartz glass substrate 4, foreach position in the Y direction of the synthetic quartz glass substrate4. That is to say, in the event that the quantity of light of the light15 and 17 is locally at or above a predetermined threshold,determination is made by the computer 27 that light 15 of a localquantity at or exceeding the threshold value has been emitted from aninterior defect 16, and identification is made of the position of theinterior defect 16 (position in the X direction and Y direction withinthe synthetic quartz glass substrate 4), and further of the type ofinterior defect 16 (regional striae, inclusions, foreign matter) fromthe shape and so forth of the light 15 of the local light quantity fromthe interior defect 16.

For example, in the event that there is regional striae or inclusionspresent in the synthetic quartz glass substrate 4 as a defect 16,introducing the ArF excimer laser light from the laser irradiationdevice 21 to the synthetic quartz glass substrate 4 causes the regionalstriae or inclusions to emit light 15 of a local quantity of thepredetermined threshold (1000 counts) or more as illustrated in FIG.3(A), while regions of the synthetic quartz glass substrate 4 other thanthe regional striae or the inclusions emit light 17. The computer 27performs image processing analysis of the light 15 and 17 which the CCDcamera 23 has received, thereby determining from the shape of the light15 with the local quantity of the predetermined threshold or higher thatthe interior defect 16 is regional striae or inclusions, and detects theregional striae or inclusions along with the position thereof, judgingthat local striae or inclusions are present at the position where thelight 15 of the regional quantity of the predetermined threshold orhigher is situated. Now, in the case of FIG. 3(A), the horizontal axisrepresents the X directional position of the synthetic quartz glasssubstrate 4, and the vertical axis represents the quantity of light(intensity) of the light 15 and 17.

Also, in the event that there is foreign matter present in the syntheticquartz glass substrate 4 as a defect 16, introducing the ArF excimerlaser light from the laser irradiation device 21 to the synthetic quartzglass substrate 4 causes the foreign matter to emit light 15 of a localquantity of the predetermined threshold (1000 counts) or more in apredetermined range D (e.g., 20 mm to 50 mm) as shown in FIG. 3(B),while regions of the synthetic quartz glass substrate 4 other than theregional striae or the inclusions emit light 17. The computer 27performs image processing analysis of the light 15 and 17 which the CCDcamera 23 has received, thereby determining from the shape of the light15 with the local quantity of the predetermined threshold or higher thatthe interior defect 16 is foreign matter, and detects the foreign matteralong with the position thereof, judging that local striae or inclusionsare present at the position where the light 15 of the regional quantityof the predetermined threshold or higher is situated. Now, in the caseof FIG. 3(B) as well, the horizontal axis represents the X directionalposition of the synthetic quartz glass substrate 4, and the verticalaxis represents the quantity of light (intensity) of the light 15 and17.

A synthetic quartz glass substrate 4, from which interior defects 16 arenot detected by the defect detecting device 20 for the glass substrates,is subjected to precision polishing such that the principal surfaces 5and 6 are a desired surface roughness, and subjected to cleansingprocessing, thereby obtaining a mask blank glass substrate 7 (FIG. 1(c)). The roughness of the principal surfaces 5 and 6 at this time ispreferably 0.2 nm or less in root-mean-square roughness (RMS).

Now, regarding the above inspecting step, FIG. 4 illustrates therelation between the size of the ArF excimer laser light 25 and the endface 2 of the synthetic quartz glass substrate 4, as a preferablearrangement for introducing the ArF excimer laser light 25 from thelaser irradiation device 21 to the end face 2 of the synthetic quartzglass substrate 4 as shown in FIG. 2. Also, at the time of introducingthe ArF excimer laser light 25 from the laser irradiation device 21 tothe end face 2 of the synthetic quartz glass substrate 4, causativesubstance which damages the surface of the synthetic quartz glasssubstrate 4 (particularly the principal surfaces 5 and 6) uponintroduction of the ArF excimer laser light 25 is preferably eliminatedfrom the ambient atmosphere.

That is to say, as shown in FIG. 5, the laser irradiation device 21, XYZstage 22, and CCD camera 23, of the interior defect inspection device20, and the synthetic quartz glass substrate 4 which is the subject tobe inspected that is mounted on the XYZ state, are stored in the innerspace A in a clean room 41. A filter room 42 having a fan 43 and afilter (chemical filter 44 using activated carbon for example) is formedat one side of the clean room 41.

The fan 43 is formed at the base of the filter room 42. Also, thechemical filter 44 is disposed at the generally center position in thevertical direction of a partition 45 sectioning the inner space A of theclean room 41 from the filter room 42. Air which has passed through thechemical filter 44 from the fan 43 passes through a facing wall 46 whichis lattice-shaped for example, facing the partition 45, passes throughan airflow path 47 formed on the bottom of the clean room 41, and isreturned to the filter room 42 so as to be circulated. Passing the airthrough the chemical filter 44 removes causative substances such aschemical contaminants and the like which cause the above-describeddamage, so the inner space A of the clean room 41 is an atmosphere whereclean air circulates.

The inner space A of the clean room 41 having the atmosphere whereinsuch clean air is circulated is an atmosphere with a cleanliness levelhigher than ISO class 5, preferably an atmosphere with a cleanlinesslevel higher than ISO class 4, and further preferably an atmosphere witha cleanliness level higher than ISO class 3. Cleanliness as describedhere is a clean room standard stipulated in ISO 14644-1: 1999(Cleanrooms and associated controlled environments—Part 1:Classification of air cleanliness).

Thus, chemical contaminants are removed from the inner space A of theclean room 41, so contaminants in the ambient atmosphere around thesynthetic quartz glass substrate 4 loaded on the XYZ stage 22 becomeextremely rare, so adhesion or deposition of the contaminants on thesurface of the synthetic quartz glass substrate 4, particularly on theprincipal surfaces 5 and 6 which have been polished to a mirror.Accordingly, trouble can be avoided wherein adhering matter anddeposited matter which has adhered to the surface of the syntheticquartz glass substrate 4 (particularly on the principal surfaces 5 and 6which have been polished to a mirror) absorbs the ArF excimer laserlight 25 which is high-energy light and is heated, placing the surfaceof the synthetic quartz glass substrate 4 in a locally high-temperaturestate, thereby damaging the surface.

Also, the ArF excimer laser light 25 introduced to the end face 2 of thesynthetic quartz glass substrate 4 from the laser irradiation device 21in the inspection step has a beam shape which is greater than the widthW of the end face 2 as shown in FIG. 4, and is perpendicularlyintroduced to the side face 51 of the end face 2.

That is to say, the end face 2 where the ArF excimer laser light 25 isintroduced is configured having the side face 51 orthogonal to theprincipal surfaces 5 or 6 of the synthetic quartz glass substrate 4where the thin film (later-described halftone film 8) to serve as a maskpattern is formed, and chamfered faces 52 and 53 between the side face51 and the principal surfaces 5 and 6. The sum of the width W1 of theside face 51, the width W2 of the chamfered face 52, and the width W3 ofthe chamfered face 53, is the width W of the end face 2, and is, forexample W=6.85 mm. Also, the ArF excimer laser light 25 introduced tothis edge face 2 is ArF excimer laser light which has a quadrangle beamshape with a long side a×short side b (a=7.0 mm, b=4.0 mm), and power of6 mJ (accordingly, energy (per pulse) per unit area is 21.4 mJ/cm²), andfrequency of 50 Hz.

Upon such ArF excimer laser light 25 being introduced from the laserirradiation device 21 to the end face 2 of the synthetic quartz glasssubstrate 4, the energy of the ArF excimer laser light 25 per unit areaat the end face 2 is not too strong, so occurrence of plasma at the endface 2 is prevented. Moreover, the intensity of the light 15 generatedat an interior defect 16 by the ArF excimer laser light 25 introduced tothe end face 2 is sufficiently ensured to a detectable degree.Conditions for the ArF excimer laser light 25 necessary to preventplasma from occurring as described above, while also sufficientlyensuring intensity of the light 15 is energy (per pulse) of 10 mJ/cm² ormore but 50 mJ/cm² or less per unit area, and more preferably 15 mJ/cm²or more but 45 mJ/cm² or less. Also, the frequency is preferably 40 Hzor higher, in order to accurately detect interior defects 16 and improveinspection precision.

Also, the ArF excimer laser light 25 introduced to the edge face 2 hasshape which is a quadrangle shape with a long side a×short side b (a=7.0mm, b=4.0 mm), which is greater dimensions that the width W (6.85 mm) ofthe end face 2 of the synthetic quartz glass substrate 4 at the longside (a=7.0) side, so the ArF excimer laser light 25 is also irradiatedin the plane direction of the principal surfaces 5 and 6 of thesynthetic quartz glass substrate 4. Accordingly, even in the event thatparticles or contaminants 55 are adhering to the principal surfaces 5and 6, these particles and contaminants 55 are blown off by the ArFexcimer laser light 25 and can be removed. Note that while a quadrangleshape as been described for the shape of the ArF excimer laser light 25,circular or elliptical shapes having a diameter equal to or exceedingthe width W of the end face 2 may be used.

Further, as long as there is no occurrence of plasma by the energy ofthe laser light within or around the synthetic quartz glass substrate 4,the ArF excimer laser light 25 may be parallel light, light with acertain expansion, or light converging with a certain level of angle.Parallel light, or light having a slight expansion is preferable. Theexpansion angle is preferably 6 mrad or less.

Note that with the above-described embodiment, introduction of the ArFexcimer laser light to the synthetic quartz glass substrate 1 isperformed with a state wherein the synthetic quartz glass substrate 4 isprepared by polishing the principal surfaces 5 and 6 which are thesurface of the synthetic quartz glass substrate 1, and the opposing endfaces 2 and 3, to a mirror, but the synthetic quartz glass substrate 4may be in a state wherein only the end face 2 at the side where the ArFexcimer laser light is to be introduced is polished to a mirror. Also,as with another embodiment shown in FIG. 6, the synthetic quartz glasssubstrate 4 may be in a state wherein the end face 2 and the end face 18(FIG. 2) which is contiguous to the end face 2 and at which lightgenerated by the interior defect 16 is received or sensed, are polishedto a mirror. With the other embodiment shown in FIG. 6, in the stage ofFIG. 6( b), the synthetic quartz glass substrate 4 is in a state whereinthe end face 2 from which the ArF excimer laser light is introduced, andthe end face 18 which is contiguous to the end face 2 and at which lightgenerated by the interior defect 16 is received or sensed, are polishedto a mirror to a degree wherein the ArF excimer laser light can beintroduced, and light generated by the interior defect 16 can bereceived or sensed. In FIG. 6, the stages other than FIG. 6( b) areperformed in the same way as with FIG. 1.

That is to say, in the preparation step of the synthetic quartz glasssubstrate, an arrangement may be made wherein, of the surfaces of thesynthetic quartz glass substrate 4, the remaining end face 19 (FIG. 2)and the opposing principal surfaces 5 and 6 are not polished to a mirrorhad have a surface roughness of around 0.5 μm, but the aforementionedend faces 2 and 18 have a surface roughness of around 0.03 μm or less.

As described above, optical inhomogeneity of the synthetic quartz glasssubstrate 4, i.e., interior defects 16 leading to transfer patterndefects, are sensed or detected at an early stage (the stage of FIG. 6(b)) prior to precision polishing of the principal surfaces of thesynthetic quartz glass substrate 4 in the mask blank glass substratemanufacturing process, meaning that precision polishing is performed forthe principal surfaces and other end faces only for synthetic quartzglass substrate 4 in which there is no optical inhomogeneity uponintroduction of the ArF excimer laser to the synthetic quartz glasssubstrate 4, so waste in the manufacturing process of the glasssubstrate for a mask blank can be cut down on.

In the event of performing the inspection step using the ArF excimerlaser light in a state wherein the principal surface of the syntheticquartz glass substrate 4 has not been mirror polished, there is the needto sense or detect regional or local optical inhomogeneities from theend face 18 of the synthetic quartz glass substrate 4, so the inspectionstep is performed with a defect inspecting device such as shown in FIG.7. Note that in FIG. 7, components with the same configuration as inFIG. 2 will be described having been denoted with the same referencenumerals.

The defect inspecting device shown in FIG. 7 includes a laserirradiation device 21 serving as light introducing means for introducingArF excimer laser light which is light of the exposure wavelength (i.e.,light of the same wavelength as the exposure wavelength) from the endface 2 of the synthetic quartz glass substrate 4, and XYZ stage 22 uponwhich the synthetic quartz glass substrate 4 is placed in moved in the Xdirection, Y direction, and Z direction, as to the laser light emittedfrom the laser irradiation device 21, and a CCD device and a lens forwidening the detection range of the CCD device (both unshown) disposedon the end face 33 side of the synthetic quartz glass substrate 4 placedon the XYZ stage 22, and has a CCD camera (line sensor camera) 23serving as photoreceptor means having a detection field 24 over theentire range of the width direction of the synthetic quartz glasssubstrate 4 (i.e., the irradiation direction of the laser lightirradiated from the laser irradiation device 21), and a computer 27serving as detecting means, connected to the CCD camera 23 using a USBcable 26.

The laser irradiation device 21 sequentially introduces the ArF excimerlaser light from each position in the Y direction at the end face 2 ofthe synthetic quartz glass substrate 4 (i.e., the longitudinal directionof the end face 2), while the XYZ stage 22 moves the synthetic quartzglass substrate 4 in the Y direction. Accordingly, the ArF excimer laserlight 25 is scanned in the longitudinal direction (the α direction inFIG. 4(A)) of the end face 2 of the synthetic quartz glass substrate 4.Also, the CCD camera 23 receives and captures light from the end face 18side of the synthetic quartz glass substrate 4 for each position in theY direction of the synthetic quartz glass substrate 4, regarding thelight 15 and 17 having a wavelength longer than the wavelength λ1, whichthe synthetic quartz glass substrate 4 emits due to the ArF excimerlaser light (wavelength of λ1) being irradiated into each position inthe Y direction at the end face 2 of the synthetic quartz glasssubstrate 4.

Also, in the above embodiment, an example has been described wherein theArF excimer laser light 25 from the laser irradiation device 21 isperpendicularly introduced to a side face perpendicular to the principalsurfaces 5 and 6 at the end face of the synthetic quartz glass substrate4. However, an arrangement may be made wherein, following predictionpolishing of the principal surfaces 5 and 6 and the side faces (e.g.,side faces of the end faces 2 and 3) of the synthetic quartz glasssubstrate 4, ArF excimer laser light 25 is introduced into the syntheticquartz glass substrate 4 under the condition that the light isintroduced from one of the chamfered faces formed between the side facesand principal surfaces 5 and 6 to effect total reflection at theprincipal surfaces 5 and 6 and the side faces. In this case, the ArFexcimer laser light 25 becomes essentially trapped within the syntheticquartz glass substrate 4, but in the event that an adhering matter orthe like is adhering to the surface of the synthetic quartz glasssubstrate 4, the condition of total reflection does not hold, so the ArFexcimer laser light 25 leaks out, and the leaked ArF excimer laser light25 is absorbed by the adhering matter and makes a regionally or locallyhigh-temperature state on the surface of the synthetic quartz glasssubstrate 4, thereby damaging the synthetic quartz glass substrate 4. Inthis case, in the event that the synthetic quartz glass substrate 4 ison the clean atmosphere within the inner space A of the clean room 44 asshown in FIG. 5, no adhering matter adheres to the surface of thesynthetic quartz glass substrate 4, and accordingly, occurrence ofdamage can be prevented. Or, an arrangement may be made wherein,following precision polishing of the principal surfaces 5 and 6 of thesynthetic quartz glass substrate 4, the ArF excimer laser light 25 isintroduced from the principal surfaces 5 and 6.

Also, regarding introducing the ArF excimer laser light from the endface 2 of the synthetic quartz glass substrate 4 in the aboveembodiment, the four corners of the synthetic quartz glass substrate 4which is the mask blank glass substrate are round chamfered (rounded),so upon ArF excimer laser light being irradiated to the four cornersthat have been round chamfered, the lens effects of the rounded facescollect light in the synthetic quartz glass substrate 4, is the energyof the ArF excimer laser light that has been introduced becomes high,and there are cases of damage occurring at the focal point. Depending onthe focal point, damage inside the substrate causes change in opticalproperties as to the exposure light (e.g., drop of transmissivity),leading to transfer pattern defects, which is undesirable. Also,collecting the ArF excimer laser light with the rounded faces can leadto cracking of the substrate in the event that internal damage to thesubstrate is great, which is undesirable. In this case, shielding means(not shown) are preferably used to shield such that there is noirradiation of the ArF excimer laser light on the four corners of thesynthetic quartz glass substrate. Thus, internal damage to the substrateby the ArF excimer laser light by lens effects of the rounded faces canbe prevented.

Also, while ArF excimer laser, which is the same as the inspection lightand the exposure light, has been used in the above embodiment, this doesnot necessarily have to be the same as the inspection light and exposurelight, and may be laser light having a wavelength of 200 nm or shorter,or a light source with a wavelength of 200 nm or shorter. Preferable islight having a wavelength of 200 nm or shorter with transmissivity of80% or higher with regard to the synthetic quartz glass substrate whichis the mask blank glass substrate, and more preferably 85% or higher.Preferably, light with a wavelength of the 100 nm to 200 nm willsuffice, and F2 excimer laser may be used. Or, an arrangement may bemade wherein, in order to obtain light with the same wavelength as theArF excimer laser or F2 excimer laser, light from a light source such asa deuterium (D2) lamp or the like, is subjected to spectroscopy and thecentral wavelength having the same wavelength as ArF excimer laser or F2excimer laser is used. However, using the same light for the inspectionlight and exposure light is preferably, since optical inhomogeneitiesinspection can be performed under the actual pattern transferenvironment.

Also, while the above embodiment has been described using photoreceptormeans to detect optical inhomogeneities, in the event that there is noneed to identify the type of optical inhomogeneity, i.e., the type ofinterior defect 16 which would become a transfer pattern defect, theinspection step may be carried out by visual sensing of light(fluorescence) regionally or locally emitted, in a state whereinprotection is in place using a transparent acrylic material capable ofcutting out ultraviolet wavelengths which affect the human body. Also,while light 15 and 17 having a wavelength longer than the exposurewavelength light (inspection light), emitted by interior defects 16 inthe synthetic quartz glass substrate 4 and regions other than theinterior defects 16, have been described as being received with the CCDcamera 23, but an arrangement may be made wherein the inspection step isperformed by a spectroscope receiving the light 15 and 17 and measuringthe spectral properties (wavelength and intensity) of the interiordefect 16 and intensity (quantity of light) of the light 15 and 17,thereby sensing or detecting the interior defect 16. Also, anarrangement may be made wherein the inspection step is performed by acolor camera being used for the CCD camera 23, and light 15 and 17having a wavelength longer than the exposure wavelength light(inspection light), emitted by interior defects 16 in the syntheticquartz glass substrate 4 and regions other than the interior defects 16,is received and captured, the images of the CCD camera 23 are subjectedto image processing by color such as red, green, blue, and so forth, bythe computer 27, and the interior defects 16 are sensed or detectedbased on information such as the intensity (quantity of light)distribution of the light subjected to image processing by color orinformation regarding wavelength of the light or the like. Further,detection of interior defects 16 may be performed at the final stage inthe manufacturing process of the mask blank glass substrates.

Also, with above embodiment, an example has been described wherein, atthe time of introducing the ArF excimer laser light to the syntheticquartz glass substrate 4, light regionally or locally emitted by theinterior defect 16, and light emitted by regions other than the interiordefect 16 are sensed or detected, but the present invention is notrestricted to this arrangement, and the inspection step may performedwith an arrangement wherein regions other than the interior defect 16 donot emit light even upon introducing the ArF excimer laser light intothe synthetic quartz glass substrate 4, so only light regionally orlocally emitted from the interior defect 16 alone is sensed or detected.

Also, while the above embodiment described a synthetic quartz glasssubstrate used as the transparent substrate for a mask blank, in thecase of using ArF excimer laser as the exposure light, but the presentinvention is not restricted to this, an transparent quartz glassobtained by melting a quartz ingredient may be used. Also, in the eventthat the exposure light is F2 excimer laser, a calcium fluoride (CaF2)substrate or a glass substrate doped with fluorine may be used.

Also, while the above embodiment has described transparent substratesfor mask blanks to be the subject of inspection, the present inventionis not restricted to this, and in the case of the state before forming atransparent substrate for a mask blank, or a synthetic quartz glasssubstrate, inspection may be performed on articles in the state ofsynthetic quartz glass ingot in which synthetic quartz glass isgenerated, the state of blocks cut out from the synthetic quartz glassingot, or the state of plates cut our from the blocks. Also, opticalcomponents used in an exposure device used for photolithography such aslenses, or articles in the state before being worked into lenses, may bethe subject of inspection.

[B] Manufacturing Method for Mask Blank

Next, a thin film (halftone film 8) to serve as a mask pattern is formedby sputtering on the principal surface 5 of a mask blank glass substrate7, and a mask blank 9 (halftone-type phase-shift mask blank) isfabricated (FIG. 1( d)). Film formation of the halftone film 8 isperformed using a sputtering device having the following configuration,for example.

The sputtering device is a DC magnetron sputtering device 30 such asshown in FIG. 8, having a vacuum chamber 31 with a magnetron cathode 32and substrate holder 33 within the vacuum chamber 31. A sputteringtarget 35 adhered to a backing plate 34 is mounted to the magnetroncathode 32. For example, oxygen-free copper is used for the bakingplate, and indium is used for adhering the sputtering target 35 and thebacking plate 34. The backing plate 34 is either directly or indirectlycooled by a water-cooling mechanism. Also, the magnetron cathode 32,baking plate 34, and sputtering target 35 are electrically joined. Aglass substrate 7 is mounted to the substrate holder 33.

As shown in FIG. 9, the sputtering target 35 and the glass substrate 7are disposed such that the opposing faces of the glass substrate 7 andthe sputtering target 35 assume a predetermined angle (targetinclination angle) 0. Thus, a thin film (halftone film 8) to serve as amask pattern is uniformly formed on the principal surface of the glasssubstrate 7, so irregularities in transmissivity within the substrateface to serve as the mask blank can be suppressed. In this case, theoffset distance d between the sputtering target 35 (the target centerthereof) and the glass substrate 7 (the substrate center thereof) is 340mm, and the perpendicular distance (T/S) between the sputtering target35 and the glass substrate 7 is 380 mm, and the inclination angle of thesputtering target is 15°.

The vacuum chamber 31 shown in FIG. 8 is drawn using a vacuum pump froman exhaust opening 37. Following the atmosphere within the vacuumchamber 31 reaching a degree of vacuum to where there is no affect onproperties of the film to be formed, a gas mixture including nitrogen isintroduced from a gas inlet 38, and negative voltage is applied to themagnetron cathode 32 using a DC power source 39, thereby performingsputtering. The DC power source 39 has arc detecting functions, andmonitors the discharge state during sputtering. The internal pressure ofthe vacuum chamber 31 is measured by a pressure gauge 36.

[C] Manufacturing Method for Exposure Mask

Next, as shown in FIG. 1, following applying a resist on the surface ofthe halftone film 8 of the mask blank 9 (halftone-type phase-shift maskblank), heating processing is performed to form a resist film 10 (FIG.1( e)).

Next, a predetermined pattern is drawn on the resist film 10 on the maskblank 11 with the resist film, and developed, thereby forming a resistpattern 12 (FIG. 1( f)).

Next, using the resist pattern 12 as a mask, the halftone film 8 issubjected to dry etching, thereby forming a halftone film pattern 13 asa mask pattern (FIG. 1( g)).

Finally, the resist pattern 12 is removed, thereby obtaining an exposuremask 14 wherein the halftone film pattern 13 is formed on the glasssubstrate 7 (FIG. 1( h)).

Note that while with the above embodiment, description has been madewith regard to halftone-type phase-shift mask blanks wherein halftonefilm is formed on a glass substrate for a mask blank, and halftone-typephase-shift masks wherein halftone film patterns are formed on glasssubstrates for mask blanks, but the present invention is not restrictedto these. For example, a halftone-type phase-shift mask blank wherein ahalftone film is formed on a mask blank glass substrate 7 and an opaquefilm is formed on the half tone film may be formed. Also, this may be ahalftone-type phase-shift mask wherein an opaque film pattern is formedfor increasing shielding functions at desired positions on the halftonefilm pattern, used as a halftone-type phase-shift mask obtained fromthis halftone-type phase-shift mask blank.

Also, this may be a photo-mask blank wherein an opaque film is formed onthe mask blank glass substrate 7, or a blank for chromium-free use,wherein a thin film for forming a mask pattern for fabricating achromium-free mask is formed by forming a lowered and raised pattern byengraving the surface of a mask blank glass substrate by etching to adesired depth.

Note that in the event that optical inhomogeneities exist in atransparent substrate for a mask blank, the advantages of the presentinvention are more clearly manifested with an inspection method of atransparent substrate for a phase-shift mask blank where effects of thetransfer pattern due to change in optical properties with regard toexposure light, and the manufacturing method for a transparent substratefor a phase-shift mask blank. Most particularly, the advantages of thepresent invention are further clearly manifested with an inspectionmethod of a transparent substrate and manufacturing method of atransparent substrate for a phase shift mask wherein the transmissivityof the mask pattern of an exposure mask with regard to the exposurelight is 10% or more (e.g., a tri-tone type phase-shift mask wherein ahalftone film having 10% or higher transmissivity with regard to theexposure light and an opaque film have been formed, or a chromium-lesstype phase-shift mask).

Note that the phase-shift mask blank such as these halftone-typephase-shift mask blanks or chromium-less mask blanks, and photomaskblanks, may be mask blanks with resist, wherein a thin film for forminga mask pattern has been formed and a resist film has been formed on thethin film for forming a mask pattern.

[D] Manufacturing Method for Semiconductor Device

The obtained exposure mask 14 is mounted in an exposure device, theexposure mask 14 is used to transfer the mask pattern of the exposuremask onto a resist film formed on a semiconductor substrate(semiconductor wafer) using photolithography with ArF excimer laser asthe exposure light, so as to form a desired circuit pattern on thesemiconductor substrate, thereby manufacturing a semiconductor device.

[E] Advantages

Due to the above configuration, the above-described embodiment has thefollowing advantages.

(1) With a defect inspecting device 20 of transparent articles such asglass articles, ArF excimer laser light which is an inspection lighthaving a wavelength of 200 nm or shorter (and which also is the exposurelight wavelength) is introduced by a laser irradiation device 21 whichis light introducing means, from a surface (end face 2) of a syntheticquartz glass substrate 4 which is a transparent article, light 15 havinga wavelength longer than the above wavelength emitted from an interiordefect 16 within the synthetic quartz glass substrate 4 and light 17having a wavelength longer than the above wavelength emitted fromregions within the synthetic quartz glass substrate 4 other than theinterior defect 16 are received by a CCD camera 23 which isphotoreceptor means from a principal surface of the synthetic quartzglass substrate 4 or an end face 33 which is different from the end face2, a computer 27 which is detecting means subjects the received light 15and 17 to image processing, and detects interior defects 16 within thesynthetic quartz glass substrate 4 based on difference in quantity oflight between the light 15 and light 17. Using light having a wavelengthof 200 nm or shorter for inspection of interior defects 16 of thesynthetic quartz glass substrate 4 which is a transparent article usedin photolithography in this way allows the interior defects 16 to bedetected well.

(2) ArF excimer laser light which is an inspection light having awavelength of 200 nm or shorter (and which also is the exposure lightwavelength) is introduced from the end face 2 of a synthetic quartzglass substrate 4 which is a transparent substrate for a mask blank,light 15 having a wavelength longer than the above wavelength emittedfrom an interior defect 16 which is a regional optical inhomogeneity ofthe synthetic quartz glass substrate 4 and light 17 having a wavelengthlonger than the above wavelength emitted from regions within thesynthetic quartz glass substrate 4 other than the interior defect 16,are received from a principal surface of the synthetic quartz glasssubstrate 4 or an end face 33 which is different from the end face 2,interior defects 16 are detected based on difference in quantity oflight between the received light 15 and light 17, and mask blank glasssubstrates 7 are manufactured using synthetic quartz glass substrates 4from which no interior defects 16 have been detected. Consequently,there are no interior defects 16 in glass substrates 7 of exposure masks14 manufactured from the mask blank glass substrates 7 via mask blanks9. Accordingly, there are no regions in the exposure masks 14 whereoptical properties locally change (e.g., drop of transmissivity) due tointerior defects 16 of the glass substrate 7, so excellent transferprecision can be had without adverse affects on pattern transfer causingtransfer pattern defects.

(3) The defect inspecting device 20 is used to detect interior defects16 in the synthetic quartz glass substrates 4 at an early stage in themanufacturing process of the mask blank glass substrate which is atransparent substrate 7 for a mask blank, prior to precision polishingof the principal surfaces 5 and 6, so the principal surfaces 5 and 6 aresubjected to precision polishing only for synthetic quartz glasssubstrates 4 with no interior defects 16, and the waste of precisionpolishing of the principal surfaces 5 and 6 of synthetic quartz glasssubstrates 4 with interior defects 16 can be cut out.

(4) ArF excimer laser light which is an inspection light having awavelength of 200 nm or shorter (and which also is the exposure lightwavelength) is introduced to a synthetic quartz glass substrate 4 whichis a transparent substrate for a mask blank, and inspection for interiordefects 16 of the glass substrate is performed. Accordingly, interiordefects 16 which would be transfer pattern defects at the time ofpattern transfer using the exposure mask 14, manufactured from thesynthetic quartz glass substrate 4 via the mask blank glass substrate 7and mask blank 9, and the exposure light, can be detected well. Thesynthetic quartz glass substrates 4 from which no interior defects 16are detected and wherein there is no damage on the principal surfaces 5and 6 are used to manufacture the mask blank glass substrate 7, so thereare no regions in the exposure masks 14 using the mask blank glasssubstrates 7 wherein optical properties regionally or locally change(e.g., drop of transmissivity) due to interior defects 16 in the glasssubstrate or damage to the principal surfaces 5 and 6, so no transferpattern defects occur, and transfer precision can be improved.

(5) In the interior defect 16 detecting step, the synthetic quartz glasssubstrate 4 which is the inspection subject, has been placed in theinternal space A of a clean room 41 through which clean air circulates,so at the time of introducing the ArF excimer laser light 25 which isinspection light, into the synthetic quartz glass substrate 4, the ArFexcimer laser light 25 can be introduced to the synthetic quartz glasssubstrate 4 in the state wherein causative substance which causes damageto the surface (particularly principal surfaces 5 and 6) of the glasssubstrate 4 at the time of introducing the ArF excimer laser light 25has been eliminated from the ambient atmosphere of the synthetic quartzglass substrate 4. Consequently, damage to the surface due to adheringmatter and deposited matter adhering to the surfaces (particularly theprincipal surfaces 5 and 6) of the synthetic quartz glass substrate 4absorbing the ArF excimer laser light 25 and making the temperature ofthe surface regionally or locally high, can be prevented.

(6) The beam shape (quadrangle shape, long side a×sort side b) of theArF excimer laser light 25 introduced to the end face 2 of the syntheticquartz glass substrate 4 which is a transparent substrate for a maskblank, has been set larger than the width W of the end face 2 from whichthe ArF excimer laser light 25 is introduced, so the energy (per pulse)of the laser light 25 per unit area at the end face 2 is not too strong,so occurrence of plasma at the end face 2 can be avoided. Consequently,a situation wherein contamination or foreign matter adhering to the endface 2 damages the end face 2 by plasma can be prevented, and detectionprocession of interior defects 16 can be improved.

(7) The energy (per pulse) per unit area of the ArF excimer laser light25 introduced to the end face 2 of the synthetic quartz glass substrate4 which is a transparent substrate for a mask blank is 10 mJ/cm² or morebut 50 mJ/cm² or less, so occurrence of plasma at the end face 2 due tothe ArF excimer laser light 25 can be avoided, and also the intensity ofthe light 15 and 17 generated at interior defects 16 within thesynthetic quartz glass substrate 4 due to introduction of the ArFexcimer laser light 25 is sufficiently ensured, and accordinglyreliability of defect detection precision can be maintained.

(8) The of the ArF excimer laser light 25 introduced to the end face 2of the synthetic quartz glass substrate 4 which is a transparentsubstrate for a mask blank has a beam shape (quadrangle shape, long sidea×sort side b) larger than the width W of the end face 2, and furtherthe ArF excimer laser light 25 is scanned in the longitudinal direction(the α direction in FIG. 4(A)) of the end face 2 of the synthetic quartzglass substrate 4, so the ArF excimer laser light 25 is irradiated onboth principal surfaces 5 and 6 contiguous to the end face 2.Accordingly, particles and contaminants 55 adhering to both principalsurfaces 5 and 6 can be removed by the ArF excimer laser light 25.

First Embodiment

A synthetic quartz glass substrate obtained by being cut out to a sizeof 152.4 mm×152.4 mm×6.85 mm from synthetic quartz glass base material(synthetic quartz glass ingot) generated with silicon tetrachloride andso forth as the starting material was shaped and chamfered, whereby tensynthetic quartz glass substrates having surface roughness of the endface where ArF excimer laser light (wavelength: 193 nm) which is theinspection light is to be introduced (the side orthogonal to theprincipal surface where the thin film is formed, and chamfered faceformed between the principal surface and the side face) of a maximumheight Rmax of 0.5 μm or less, were obtained. Note that the principalsurfaces of the synthetic quartz glass substrates have not yet beensubjected to mirror polishing or precision polishing, and according arein a frosted-glass state.

Next, the defect inspecting device described in the above embodiment wasused to introduce ArF excimer laser light with a beam shape of 7.0mm×4.0 mm which is larger than the thickness of the synthetic quartzglass substrate, energy per pulse of 6 mJ, and frequency of 50 Hz, tothe end face of the synthetic quartz glass substrate, and inspection ofinner defects was performed.

Observation of interior defects of the synthetic quartz glass substratewere performed by visually observing from another end face which differsfrom the end face from which the ArF excimer laser light was introduced,and which is orthogonal to the optical path of the ArF excimer laserlight.

As a result of interior defect inspection of the synthetic quartz glasssubstrates, four of the ten exhibited regionally or locally shininginhomogeneous regions, in dot shapes, elliptical shapes, orcracked-stratum shapes. The dot-shaped light was confirmed aslight-bluish fluorescence, the elliptically shaped light as light-bluishfluorescence and yellowish fluorescence, and the cracked-stratum shapedlight as yellowish fluorescence.

The synthetic quartz glass substrates regarding which regionally orlocally shining inhomogeneous regions were not confirmed were subjectedto precision polishing of the principal surfaces and end faces (sidefaces and chamfered faces), thereby obtaining glass substrates for maskblanks.

The physical properties of the obtained glass substrates for mask blankswere measured with a transmissivity measurement system at nine positionsin the thickness direction in the mask pattern formation region (132mm×132 mm) of the glass substrates, for transmissivity of a wavelengthof 193 nm. The difference between maximum transmissivity and minimumtransmissivity was within 2% (i.e., optical loss of the glass substrateswas within 3%/cm), which is excellent. Note that measurement oftransmissivity was performed by irradiating measurement light of adeuterium lamp (wavelength of 193 nm) and calculating from thedifference between incident light quantity and output light quantity ofthe inspection light.

The glass substrates for mask blanks were used to fabricate three eachof a high-transmissivity halftone-type phase-shift mask blank formed bysequentially forming a halftone film having transmissivity of 20% as toArF excimer laser light and phase difference of 180°, an opaque filmwith optical concentration of 3 or higher, and a resist film, and aphoto-mask blank formed by sequentially forming a shield film withoptical concentration of 3 or higher as to ArF excimer laser light, anda resist film.

A halftone-type phase-shift mask was fabricated from the halftone-typephase-shift mask blank, and a photomask from the photomask blank.

The fabricated halftone-type phase-shift mask and photomask were eachmounted to an exposure device (stepper) using ArF excimer laser(wavelength of 193 nm) as the exposure light source, and circuitpatterns were formed on a semiconductor substrate, thereby fabricatingsemiconductor devices.

The obtained semiconductor devices had no circuit pattern defects andwere all satisfactory.

As described above, synthetic quartz glass substrates with no interiordefects, where transmissivity deteriorates, present in the syntheticquartz glass substrates, can be selected at the stage prior to precisionpolishing of the principal surface in the manufacturing process of glasssubstrates for mask blanks, and precision polishing can be performedonly for the principal surfaces of the selected synthetic quartz glasssubstrates to manufacture glass substrates for mask blanks. Accordingly,with the inspection method according to the present invention, precisionpolishing of synthetic quartz glass substrates with interior defects canbe avoided, so waste can be cut out.

Comparative Embodiment

On the other hand, in order to make a comparison with the aboveembodiment, a halftone-type phase-shift mask blank and a photomask blankwere fabricated using synthetic quartz glass substrates in whichfluorescence, where light is locally emitted, had been confirmed in theabove inspection step, in the same way as described above, followingwhich a halftone-type phase-shift mask and a photomask were respectivelyfabricated. Circuit patterns were formed on a semiconductor substrate byphotolithography in the same way as above using the fabricatedhalftone-type phase-shift mask and photomask, which resulted in patterndefects such as circuit patterns not being formed.

The above photomask was evaluated regarding transfer properties, using aMicrolithography Simulation Microscope AIMS 193 (manufactured by CarlZeiss), wherein was confirmed drop of transmissivity of approximately 5%to approximately 40% in regions (in the order to tens of μm to hundredsof μm) which had been locally emitting light as fluorescence.

Second Embodiment

The inspection of synthetic quartz glass substrates was performed in thesame way with the above first embodiment, other than interior defects ofthe synthetic quartz glass substrates being inspected using a defectdetecting device placed in an atmosphere where clean air circulates (ISOclass 4, using chemical filter), and further, precision polishing of theprincipal surfaces was performed, thereby obtaining glass substrates formask blanks. Consequently, inspection of interior defects of thesynthetic quartz glass substrates was performed without any damage tothe end face from which the ArF excimer laser light is introduced, andsynthetic quartz glass substrates in which local fluorescence light isnot emitted were selected. The principal surfaces of the selectedsynthetic quartz glass substrates were subjected to precision polishingand glass substrates for mask blanks were manufactured, and further, ahalftone-type phase-shift mask blank and a photomask blank werefabricated, with which semiconductor devices were fabricated byphotolithography, with no circuit pattern defects occurring.

Third Embodiment

An introduction face for introducing ArF excimer laser light was formedon synthetic quartz glass base material (synthetic quartz glass ingot)generated with silicon tetrachloride and so forth as the startingmaterial, and ArF excimer laser light was introduced from theintroduction face to inspect the interior of the synthetic quartz glassbase material for inner defects. Note that the introduction face wasformed by locally mirror polishing the surface of the synthetic quartzglass base material so as to obtain a mirror face of a size larger thanthe beam shape of the ArF excimer laser light.

Regions not locally emitting fluorescence at the time of introducing theArF excimer laser light to the synthetic quartz glass base material wereidentified, and synthetic quartz glass blocks were cut out only from theidentified regions, from which lenses for an exposure device (stepper)using the ArF excimer laser as the exposure light source, and glasssubstrates for mask blanks, were fabricated.

The obtained lenses and glass substrates for mask blanks were evaluatedregarding any drop of transmissivity of the ArF excimer laser light. Thearticles were excellent with almost not drop of transmissivity at all,such that there is no problem in use as lenses for an exposure device(stepper) and glass substrates for mask blanks.

Fourth Embodiment

Photomasks and further semiconductor devices were fabricated in the sameway as with the first embodiment, except for fabricating a photomaskblank by sequentially forming an opaque film with optical concentrationof 3 or higher as to ArF excimer laser light, and a resist film, on aglass substrate of which the transmissivity in the thickness directionof a synthetic quartz glass substrate, selected in the above-describedinspection step in the above first embodiment, was within 5% for thedifference between maximum transmissivity and minimum transmissivity(i.e., optical loss of the glass substrate of 8%/cm or less). Thesemiconductor devices obtained as a result were all excellent with nocircuit pattern defects.

Referential Example

Interior defects of synthetic quartz glass substrates were inspected forin the same way as with the second embodiment, except for performinginspection of interior defects of the synthetic quartz glass substratein the second embodiment using a defect inspection device placed in theatmosphere with no cleanliness management.

As a result, plasma occurred around the end face during irradiation ofthe ArF excimer laser light at the end face of the synthetic quartzglass substrate, and damaged the end face of the synthetic quartz glasssubstrate. Such damage is undesirable since it leads to dusting, whichin turn causes mask pattern defects, in the mask blank manufacturingprocesses, or at the time of storing the mask blanks in storagecontainers, or at the time of transporting mask blanks, in the eventthat precision polishing of the end face is not performed in thesubsequent mask blank manufacturing processing, or in cases whereinprecision polishing of the end face is performed but damage is deep andthe working margin for precision polishing of the end face is small.Note that in the event that damage is not deep and the working marginfor precision polishing of the end face is greater, this does not leadto the above dusting and is not problematic.

1. A transparent substrate for a mask blank, wherein upon introductionof light having a wavelength of 200 nm or shorter from one side of thesurface of said transparent substrate, the loss of light having awavelength longer than said wavelength that is generated regionally orlocally within said transparent substrate is 8%/cm or lower within themask pattern formation region of said transparent substrate.
 2. Thetransparent substrate for a mask blank according to claim 1, whereinsaid transparent substrate for a mask blank is a transparent substratefor a phase-shift mask blank.
 3. The transparent substrate for a maskblank according to claim 2, wherein the loss of light having awavelength longer than said wavelength that is generated regionally orlocally within said transparent substrate is 3%/cm or lower within themask pattern formation region of said transparent substrate.
 4. A maskblank, wherein a thin film to serve as a mask pattern, or a thin filmfor forming a mask pattern, is formed on the principal surface of saidtransparent substrate for a mask blank according to claim
 1. 5. Anexposure mask wherein said thin film to serve as a mask pattern on themask blank according to claim 4 is patterned to form a mask pattern of athin film pattern on the principal surface of said transparent substratefor a mask blank.
 6. An exposure mask wherein said thin film to form amask pattern on the mask blank according to claim 4 is patterned to forma thin film pattern, and the thin film pattern is used as a mask to etchsaid transparent substrate for a mask blank, thereby forming a maskpattern on the principal surface of said transparent substrate.
 7. Aphase shift mask blank for use in manufacturing a phase shift mask thatis exposed to exposure light not longer than a wavelength of 200 nm,comprising: a transparent substrate; and a semi-transparent film on thetransparent substrate; wherein an interior defect of the transparentsubstrate is not detected when defect inspection is performed byintroducing, into the transparent substrate, inspection light having thesame wavelength as the exposure light and by monitoring light emittedfrom an interior defect that would be present in the transparentsubstrate; and wherein the semi-transparent film has a transmissionfactor (transmissivity) which is not less than 10% for the exposurelight.
 8. A transparent substrate for a mask blank, wherein uponintroduction of light having a wavelength of 200 nm or shorter from aprincipal surface of said transparent substrate, the loss of lighthaving a wavelength longer than said wavelength that is generatedregionally or locally within said transparent substrate is 8%/cm orlower within a mask pattern formation region of said transparentsubstrate.
 9. The transparent substrate for a mask blank according toclaim 8, wherein said transparent substrate for a mask blank is atransparent substrate for a phase-shift mask blank.
 10. The transparentsubstrate for a mask blank according to claim 9, wherein the loss oflight having a wavelength longer than said wavelength that is generatedregionally or locally within said transparent substrate is 3%/cm orlower within the mask pattern formation region of said transparentsubstrate.
 11. The transparent substrate for a mask blank according toclaim 8, wherein said transparent substrate for a mask blank is formedof synthetic quartz glass.
 12. A mask blank comprising: a transparentsubstrate, wherein upon introduction of light having a wavelength of 200nm or shorter from a principal surface of said transparent substrate,the loss of light having a wavelength longer than said wavelength thatis generated regionally or locally within said transparent substrate is8%/cm or lower within a mask pattern formation region of saidtransparent substrate; and a thin film to serve as a mask pattern, or athin film for forming a mask pattern, formed on the principal surface ofsaid transparent substrate.
 13. The mask blank according to claim 12,wherein said mask blank is a phase-shift mask blank, and wherein theloss of light having a wavelength longer than said wavelength that isgenerated regionally or locally within said transparent substrate is3%/cm or lower within the mask pattern formation region of saidtransparent substrate.
 14. The mask blank according to claim 12, whereinsaid mask blank is a phase-shift mask blank, and wherein transmissivityof the thin film with regard to an exposure light is 10% or more. 15.The mask blank according to claim 12, further comprising a resist filmformed on the thin film.
 16. An exposure mask comprising: a transparentsubstrate, wherein upon introduction of light having a wavelength of 200nm or shorter from a principal surface of said transparent substrate,the loss of light having a wavelength longer than said wavelength thatis generated regionally or locally within said transparent substrate is8%/cm or lower within a mask pattern formation region of saidtransparent substrate; and a mask pattern of a thin film pattern formedon the principal surface of said transparent substrate.
 17. The exposuremask according to claim 16, wherein said exposure mask is a phase-shiftmask, and wherein transmissivity of the mask pattern with regard to anexposure light is 10% or more.
 18. An exposure mask comprising: atransparent substrate, wherein upon introduction of light having awavelength of 200 nm or shorter from a principal surface of saidtransparent substrate, the loss of light having a wavelength longer thansaid wavelength that is generated regionally or locally within saidtransparent substrate is 8%/cm or lower within a mask pattern formationregion of said transparent substrate; and a mask pattern formed on theprincipal surface of said transparent substrate by etching saidtransparent substrate.
 19. The exposure mask according to claim 18,wherein said exposure mask is a phase-shift mask, and whereintransmissivity of the mask pattern with regard to an exposure light is10% or more.
 20. A phase shift mask blank for use in manufacturing aphase shift mask that is exposed to an exposure light not longer than awavelength of 200 nm, comprising: a transparent substrate; and asemi-transparent film on a principal surface of the transparentsubstrate; wherein an interior defect of the transparent substrate isnot detected when defect inspection is performed by introducing, intothe transparent substrate, inspection light having the same wavelengthas the exposure light and by monitoring fluorescence emitted from aninterior defect that would be present in the transparent substrate; andwherein the semi-transparent film has a transmissivity which is not lessthan 10% for the exposure light.
 21. The phase shift mask blankaccording to claim 20, wherein upon introduction of light having awavelength of 200 nm or shorter from the principal surface of saidtransparent substrate, the loss of the fluorescence is 3%/cm or lowerwithin a mask pattern formation region of said transparent substrate.22. The phase shift mask blank according to claim 20, further comprisingan opaque film on the semi-transparent film.
 23. The phase shift maskblank according to claim 22, further comprising a resist film on theopaque film.
 24. A phase shift mask that is exposed to an exposure lightnot longer than a wavelength of 200 nm, comprising: a transparentsubstrate; and a mask pattern of a thin film pattern formed on aprincipal surface of said transparent substrate; wherein an interiordefect of the transparent substrate is not detected when defectinspection is performed by introducing, into the transparent substrate,inspection light having the same wavelength as the exposure light and bymonitoring fluorescence emitted from an interior defect that would bepresent in the transparent substrate; and wherein the mask pattern has atransmissivity which is not less than 10% for the exposure light. 25.The phase shift mask according to claim 24, wherein upon introduction oflight having a wavelength of 200 nm or shorter from the principalsurface of said transparent substrate, the loss of the fluorescence is3%/cm or lower within a mask pattern formation region of saidtransparent substrate.
 26. A phase shift mask that is exposed to anexposure light not longer than a wavelength of 200 nm, comprising: atransparent substrate; and a mask pattern formed on the principalsurface of said transparent substrate by etching said transparentsubstrate; wherein an interior defect of the transparent substrate isnot detected when defect inspection is performed by introducing, intothe transparent substrate, inspection light having the same wavelengthas the exposure light and by monitoring fluorescence emitted from aninterior defect that would be present in the transparent substrate; andwherein the mask pattern has a transmissivity which is not less than 10%for the exposure light.
 27. The phase shift mask according to claim 26,wherein upon introduction of light having a wavelength of 200 nm orshorter from the principal surface of said transparent substrate, theloss of the fluorescence is 3%/cm or lower within a mask patternformation region of said transparent substrate.